The present invention relates to a roller conveyor, and especially a roller conveyor in which a plurality of rollers between a pair of conveyor frames are driven by rotation driving means so that materials may be conveyed.
A roller conveyor for conveying materials on rollers is known in FIG. 8, which is a sectional view of a roller 101 between a pair of conveyor frames. In a roller body 102 for conveying materials, a driving force is connected and disconnected by a sprocket 103 driven by separate rotation driving means (not shown) via a pneumatic clutch mechanism 104.
The pneumatic clutch mechanism 104 comprises a tubular member 107 which is rotatably mounted to a roller shaft 105 via a bearing 106, and an elastic tube 108 between the tubular member 107 and the roller body 102. The elastic tube 108 is expanded by air pressure introduced through a conduit 105a in the roller shaft 105, and an outer surface 103A at one end of the sprocket 103 is connected with an inner surface 102A of the roller body 102 via the elastic tube 108. Thus, when the pneumatic clutch mechanism 104 is actuated, a rotational force of the sprocket 103 is transmitted to the roller body 102. To stop rotation of the roller body 102, air supplied into the elastic tube 108 is exhausted by switching of a valve.
To control driving and stop of a roller body in a roller conveyor, a linear motor is also known, in which a roller body has a magnetic material and a plurality of driving coils by which N- and S-pole magnetic fluxes can be ejected on a floor.
However, in a device which comprises the pneumatic clutch mechanism 104 as shown in FIG. 8, it is necessary to control supply and exhaustion of air in each of the roller bodies depending on connection and disconnection of driving force to the roller bodies. Therefore, it is necessary to provide conduits or supply/exhaution control valve to make a system itself complicate.
In the linear motor, owing to difference of driving system, it is not possible to use known driving force transmission means, such as a belt and a chain, which not only lead increase in cost but also require control means for switching a magnetic flux signal to each of the rollers to drive and stop the roller bodies.
In the meantime, there are a two types of roller conveyors in FIGS. 9a and 9b. In FIG. 9a, 201 denotes a rotary shaft driven by a motor and has a plurality of driving pulleys 203 fixed thereon, corresponding to rollers 202. A belt 204 is provided between the driving pulley 203 and the roller 202, and the roller 202b is driven by the rotary shaft 201 via the belt 204 to convey materials xe2x80x9cAxe2x80x9d, xe2x80x9cBxe2x80x9d, xe2x80x9cCxe2x80x9d, xe2x80x9cDxe2x80x9d.
FIG. 9a illustrates eighteen rolls from 202-a to 202-r, and each four rolls are simultaneously braked. Four rolls 202-a, 202-b, 202-c, 202-d are braked by a brake 205-1. Next four rolls 202-e to 202-h are braked by a brake 205-2 as well. Therefore, the materials xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d stop. On the contrary, the remaining rolls 202-l to 202-r are not braked since brakes 205-3, 205-4 are lower, so that the materials xe2x80x9cCxe2x80x9d and xe2x80x9cDxe2x80x9d are conveyed.
In the roller conveyor in FIG. 9b, a belt 208 is turned by rotation of a drive pulley 207, and a plurality of rollers 209 which are frictionally engaged on the belt 208 are rotated by rotation of the belt 208. Frictional engagement and disengagement between the belt 208 and the roller 209 are controlled by a clutch roll 210. As shown in FIG. 7b, the clutch rolls 210-1 and 210-2 are disposed at lower position, and the belt 208 is not engaged with the roller 209. The rollers 209-a to 209-i are disengaged from the rotation driving means 207, 208 and therefore act as free rollers which are freely rotatable in either direction. The remaining rollers 209-j to 209-r which are contacted on the belt 208 can be driven since clutch rolls 210-3, 210-4 are disposed at higher position. In this situation, the clutch roll 210-3 is lowered and disengaged from the belt 208, so that the material xe2x80x9cDxe2x80x9d is rolled on the rollers which are freely rotatable and can be arranged to contact the rear end of stopped material xe2x80x9cCxe2x80x9d.
However, in the roller conveyor as shown in FIG. 9a, when the brake 205 is actuated, the roller 202 stops after it rotates by inertia force, so that the material xe2x80x9cCxe2x80x9d and xe2x80x9cDxe2x80x9d go forward to xe2x80x9cCxe2x80x2xe2x80x9d and xe2x80x9cDxe2x80x2xe2x80x9d which stop. The materials xe2x80x9cAxe2x80x9d, xe2x80x9cBxe2x80x9d, xe2x80x9cCxe2x80x9d, xe2x80x9cDxe2x80x9d are arranged with spaces, so that they are not able to be arranged in forward-contacted position.
In the roller conveyor as shown in FIG. 9b, the roller 209 can be shifted to a driving or free roll by action of the clutch roll 210, so that a material can be arranged to contact the rear end of stopped material. However, the belt 208 must be driven by full power and it is necessary to provide a conveyor belt having length corresponding to conveying distance of the roller conveyor.
In view of the foregoing disadvantages, it is an object of the present invention to provide a roller conveyor which allows driving and stopping of a roller body without special equipment or control means, the roller conveyor being functioned as a free roller rotatable in either direction when a roller body stops.
It is another object of the present invention to provide a roller conveyor which is easily variable in length and can be readily shifted between driving and free conditions, conveyed materials being able to be arranged in forward-contact position.
In order to achieve the objects, according to one aspect of the present invention, there is provided a roller conveyor comprising:
a pair of conveyor frames;
a plurality of rollers which are rotatably mounted between said pair of conveyor frames; and
rotation driving means for driving a roller or a set of rollers in the plurality of rollers to-convey materials, the roller or the set of rollers being able to be transformed to a free roller or rollers which are rotatable in either direction by an external force when said rotation driving means stop.
According to another aspect of the present invention, there is provided a roller conveyor comprising:
a pair of conveyor frames;
a plurality of rollers which are rotatably mounted between said pair of conveyor frames; and
rotation driving means for driving the rollers to covey materials, each of the rollers comprising a roller body which is rotatably mounted on a stationary roller shaft, and a driving force receiver which receives a rotational force from said rotation driving means, said roller conveyor further comprising driving force transmitting means for transmitting said rotational force to said roller body only when said driving force receiver receives the rotational force.